By Tom Miles and Stephanie Nebehay

GENEVA (Reuters) – The United Nations will take the “last resort” option of air drops of humanitarian aid if access to besieged areas in Syria is not improved by June 1, U.N. Syria envoy Staffan de Mistura said on Thursday.

Without improved aid access and some restoration of Syria’s tattered cessation of hostilities, the credibility of the next round of peace talks would be in question, he said.

The damage to the peace talks prompted the United States and Russia to convene the International Syria Support Group of major and regional powers on Tuesday, which toughened the truce terms and endorsed a stronger push for humanitarian aid.

“We want to bring aid to everyone. If the food cannot be brought by convoys, the alternative is air drops,” de Mistura told reporters.

Air drops were “the most expensive, the most complicated, the most dangerous option”, he added. “So the air drops are the last resort, but we are getting close to it.”

The U.N.’s World Food Programme (WFP) has made 35 air drops of food and other supplies to about 100,000 people in the eastern town of Deir al-Zor, besieged by Islamic State, due to a total lack of access, but that is the only location so far.

The International Committee of the Red Cross (ICRC), in a position paper given to donors on Wednesday and obtained by Reuters, voiced deep concerns about air drops and urged states to consider the risks and consequences.

“Air drops in certain contexts, particularly populated, urban environments such as many of those areas under siege in Syria, can pose a real, physical danger to persons to whom they are intended to provide relief,” the ICRC said.

“To avoid causing unnecessary injuries, and to ensure the orderly, non-violent distribution of the assistance, the drop zone must be adequately controlled.”

Air drops should not substitute the need for ground-based aid, it added.

CREDIBILITY OF TALKS

De Mistura said he would not abandon the peace talks, but was waiting for the right date.

“Obviously we are in a clear hurry to start reintroducing the next round of the intra-Syrian talks,” he said.

He did not rule out overriding any Syrian government objections to air drops, but said it would depend on U.N., U.S. and Russian assessments.

De Mistura’s humanitarian advisor Jan Egeland said a clear intention to organise air drops for Syria’s remaining besieged areas would help convince President Bashar al-Assad to allow humanitarian convoys to go in by road.

“We do believe that the option of air drops will actually make it possible for us to go by land in the next weeks,” he said.Egeland said aid had reached 13 of 18 besieged areas after a convoy got into the Harasta suburb of Damascus on Wednesday. But another convoy was turned back from Daraya town last week because what he called “well-fed” soldiers barred it from delivering baby milk powder.

Humanitarian supplies this month have not reached half the 900,000 people the U.N. wanted to supply in besieged and hard-to-reach areas, he said. The target for June is 1.1 million.

(Reporting by Tom Miles and Stephanie Nebehay; Editing by Tom Heneghan)